Marine vessels have heretofore been provided with integral bow or side thrusters to improve the maneuvering thereof during stationary slow speed operations, such as docking or fishing. Such thrusters include a tunnel formed athwartship in the vessel within which is mounted a propeller. Power is transmitted to the propeller from a source disposed within the vessel's hull. Such heretofore proposed thrusters are expensive to install, create considerable drag during forward movement of the vessel and are difficult to maintain. Moreover, such thrusters are subject to marine growth. Additionally, since such heretofore proposed thrusters are located below the waterline they cannot be repaired or otherwise maintained except when the vessel is in drydock.